On the basis of work conducted in our lab and in other labs, we have proposed that male copulatory behavior of the rat is controlled, in part, by a neural system which includes the medial preoptic area (mPOA), the medial forebrain bundle (MFB) of the hypothalamus and midbrain extensions of the MFB. The overall objectives of this project is to submit this hypothesis to rigorous testing at three levels of analysis: 1) anatomical, 2) behavioral and 3) neurochemical. We plan to interrupt this proposed system at several levels along its telencephalic-hypothalamic-midbrain extension in an attempt to further identify the critical connections. Preparations which result in sexual deficits will be compared and contrasted in terms of the nature of the behavioral impairment being produced. A series of behavioral tests designed to identify subtly changes in the males' responsiveness to sexual stimuli are being developed for this purpose. Finally, since this proposed system includes major projections from ascending monoamine-containing pathways, neurochemical analysis of behaviorally disruptive lesions will be included.